can you delete keyframes at regular intervals in a given range?
It's not exactly what you're asking for, but maybe it can help : there is an (integrated) addon, Simplify Curves. It reduces the number of keyframes, preserving the general shape of the curve.


Activate the addon (search "simplify" and click the checkbox next to "Add Curve: Simplify Curves") 
Select your F-curves
type Spacebar then "simplify", select "simplify F-curve"
adjust the "distance error" setting. Warning, it's located in the Operator panel in the 3d view, not in the F-Curve editor